Heating unit for bituminous materials



Jan. 21, 1958 "J. A. BRbCK EI'AL 1,820,

HEATING UNIT FOR BITUMINOUS MATERIALS Filed May 9, 1955 3 Sheets-Sheet 1p .0 N, q-

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F M m N L N ,LL Q I J g INVENTORS JAMES A. BROOK BY DOYLE L.SPEAR$ATTORNEY Jan. 21, 1958 J. A. BRbcK ETAL HEATING UNIT FOR BITUMINOUSMATERIALS s Sheets-Sheet Filed May 9, 1955 ATTORNEY Jan.*2l, 1958 J. A.BROCK ETAL 2,820,451

HEATING UNIT FOR BITUMINOUS MATERIALS Filed May 9, 1955 s heets-Sheet sFIG."4

INVENTOR A JAMES A. BROOK DOYLE L. SPEARS BY W A ATTORNEY United StatesPatent 2,820,451 HEATING UNITFOR BITUMINOUS MATERIALS James A. Brock andDoyle L. Spears, Chattanooga, Tenn.; said Spears assignor to CobbleBrothers Machinery Company, Inc., Chattanooga, Tenn., a corporation ofTennessee Application May Q, 1955, Serial No. 507,016

4 Claims. (Cl. 126-3435) This invention relates to a portable heatingunit for bituminous materials and more particularly to a selfcontainedportable heating tank for bituminous materials.

Bituminous materials, such as asphalt, are customarily transported insolid form in railroad tank cars. In the bottom of these tank cars aresteam coils to which steam is introduced from a power plant when thetank car arrives at its destination. The heat from the steam coilsconverts the solid bituminous material into liquid so that it may bepumped from the tank car into a tank truck or into a stationaryreceptacle. In mixing the bituminous material with gravel to form pavingmaterial, the bituminous material must be at a temperature of about 350F. in order that it may bond properly with the gravel. When the liquidbituminous material leaves the railroad tank car, it is at approximately200 F. Consequently, it must again be heated until the temperature iselevated to the required 350 F.

Various apparatuses and methods have been employed to prepare thebituminous materials for paving operations. Most of these apparatuseshave employed two heating systems, one generally a boiler for providingsteam to the steam coils in a railroad tank car and a second heatingunit for elevating the temperature of the liquid material to 350 F.,such as a direct-fired gas or oil burner, or a jacketed oil or gasburner which supplies heat to a heat transfer medium, such as oil, whichis in turn circulated to heat the bituminous material.

Another disadvantage of present conventional heating and mixing plantsfor paving material is the fact that in highway construction such plantshave tobe frequently moved to keep pace with the progress of the highwayconstruction. The plants have to be dismantled, transported andreassembled at a new site close to the current construction operation.Because of the size of these plants, their transportation requiresapproximately a thousand man-hours, not only because of the dismantling,moving, and reassembling, but also because the heat generating plantsmust be allowed to cool before dismantling, and also must be fired upagain after reassembling. Even after the heat generating plant isretired, it requires considerable time for the thousands of gallons ofbituminous material to be heated to a temperature of 350 F.

It is therefore an object of this invention to overcome thedisadvantages enumerated and to provide a simple compact heating unitwhich will provide an economical method of heating the bituminousmaterials to the desired temperature as well as providing steam powerfor other plant operations.

Another object of this invention is to provide a large heating tankcontaining a fire tube boiler for generation of steam and which employsthe waste heat of the line gases for heating the bituminous materials.

It is a further object of this invention to provide a selfcontainedportable unit for heating bituminous material as well as generatingsteam power for other plant operations.

2,820,451 Patented Jan. 21, 1958 Further objects and advantages of theinvention will be apparent from the following description taken inconjunction with the drawing, wherein:

Fig. 1 is a side elevation with the tank, canopy, and rear platform insection along lines 1-1 of Fig. 3 and illustrating a preferredembodiment of the invention;

Fig. 2 is a section taken along the lines 22 of Fig. 1;

Fig. 3 is a rear end elevation of the apparatus disclosed in Fig. 1,with: portions of the rear axle and supporting beamsbroken away; and

Fig. 4 is a sectional view along the line 1-1 of Fig. 3.

Briefiystated the invention comprises a large portable tank forreceiving bituminous materials. Horizontally disposed within the tank isa fire tube boiler, the heat receiving end ofsaid boiler opening throughthe rear end of the tank to communicate with a combustion chamber whichis located outside the tank. The combustion chamber may be fired by anytype fuel burner, such as oil or gas. At the forward end of the boilerwithin the tank is a header for receiving the exhaust gases from theboiler tubes and distributing said gases to a plurality of stack flues.These stack flues extend subjacent to and substantially horizontallyalong the bottom of the tank and discharge into an exhaust header justoutside the rear end of the tank. It is important that these stack fiuesbe located near the bottom of the tank in order that they mayimmediately begin heating the initial portion of the bituminous materialwhich is poured into the tank. As the tankis filled, the heated portionsof the bituminous material near the bottom will rise to the top creatingconvection currents causing a uniform temperature throughout thematerialin the tank. Because the stack fines are beneath the boiler, an induceddraft fan communicating with theoutside exhaust header is necessary tocreate a draft in the combustion chamber, boiler tubes, and stack fiues.The steam generated in the boiler is released through a steam dome andexhaust valves outside the tank. There is little heat transfer betweenthe outside of the boiler and the bituminous material as compared withthe heat transfer from the stack flues. Steam coils may be includedwithin the tank to accelerate the heating of the bituminous material byutilizing a portion of the steam generated by the boiler. However, mostof the steam from the boiler is used for liquefying bituminous materialin railroad tank cars and for other plant operations, such as providingsteam to jacketed conduits for transporting the hot bituminous materialin liquid condition and supplying steam to steam-atomizing burners usedfor drying gravel before it is mixed with the bituminous material. Inthis manner the invention contemplates satisfying the heating and powerrequirements for the production of paving material from a single heatgenerating unit.

Referring now to the drawings in detail, a large tank 10 for containingliquid bituminous material has an inlet 11 near the top and an outlet 12near the bottom of the tank in the rear wall 13. Extending through therear wall 13 and horizontally disposed within the tank 10 is a fire tubeboiler 14 containing boiler tubes 15. Extending from the top of theboiler 14 and upward through the top of the tank 10 is a steam dome 16provided with steam outlets 17. A steam header 1% is mounted on the rearwall 13, having inlet 19 and outlets 20. Steam is fed from one of thedome outlets 17 through conduit 21 to inlet 19. From the header outlets20, connections are made to supply steam for power and plant operationsto be later described.

At the forward end of the broiler 14, an exhaust header 22 supportedfrom the bottom of the tank 10 by saddle bracket 23 collects the exhaustgases from the boiler tubes 15 and distributes the gases to stack flues24,-communicating with the bottom portion of the header 2;;

3 and extending horizontally back beneath the fire tube boiler 14 andnear the bottom of the tank 10, until the fines communicate with a stackflue header mounted on the outside of the rear wall 13. An induced draftfan 26 is connected to stack flue header 25 to draw the gases from thestack fiues and discharge the gases through exhaust port 28.

A cylindrical combustion chamber 29 having refractory-lined inner wallsis mounted on a frame 30 supported on rear platform 27 to communicatewith fire tube boiler 14 throu h the rear Wall 13. A heat generator suchas oil burner 31 communicating with the rear end of combustion ch mber29 provides a combustible mixture of air and oil to the combustion chmber, where the mixture is ignited and then passes through the boilertubes 15 to generate steam in the boiler 14.

To receive the return condensate from an external steam power o erationto whi h steam has been su plied from header 18, a pair of saddle tanks32 and 33 are mounted along opposite sides of the tank 10. Inlets 34 and35 re located in the ends of and near the t ps of each saddle tankrespectively, throu h which condensate is received. A feed water pump 36is mounted in saddle tank 3: and pumps water from sadd e tank 33 throughconduit 37 to the boiler 14. The saddle tanks 32 and 33 are connected byconduit 38 so that water in both tanks will be at the same level. Thelocation of the saddle tanks a ainst such a lar e exp sed surface of thetank 10 allows the water within the saddle tanks to absorb a lar equantity of heat radiating from the tank 10 which would otherwise bewasted. In this manner, the feed water is pre-heated to increase theefficiency of the boiler 14.

As a sup lemental source of heat within the tank, steam coils 40 may bearranged horizontally in the bottom of the tank 10 below the stack flues24 and supplied with steam through conduit 41 from one of the steamheader outlets 20. The condensate from the coils 40 flows throughconduit 42 to saddle tank 32.

To prevent an excessive amount of bituminous material from. falling uponthe steam coils 40 and to allow the coils to heat small quantities ofmaterial at a time, a cover plate 43 having apertures 44 is spaced abovethe coils 40 and below the stack flues 24. The apertures 44 permit smallstreams of bituminous material to flow around the coils 40. where thematerial may be further heated and circulated into the upper portion ofthe tank 10 or may be withdrawn through outlet 12.

To make the entire heating unit portable, it is mounted on a trailercomprising supporting beams 45 and 46 which extend longitudinallybeneath the rear platform 27 and the tank 10, the beams terminating attheir forward ends in a tongue 47 adapted to be connected to a primemover 48. The rear portions of the beams are supported by wheels 49. Acontrol panel 50, containing controls and gauges for regulating the lowwater, temperature, and pressure of the boiler and for regulating theburner 31 and induced draft fan 26, is located in any convenientposition and is shown in Figs. 1 and 3 mounted alongside the combustionchamber 29. A canopy 51 may extend out from the rear wall 13 to protectthe instruments, the machinery and also the operator from inclementWeather. Water glass 52 is mounted on rear wall 13 to determine thewater level in the boiler 14.

The tank 10 may also be provided with a fuel reservoir 53 located in theforward end of the tank 10 to provide fuel to the burner 31 throughconduit 54. The reservoir is provided with fuel inlet 55.

The operation of the heating unit is as follows:

The portable unit may be moved to a position adjacent a railroad sidingin order that its boiler may generate sufficient steam to melt thebituminous material in a railroad tank car standing on the siding, andto receive the liquid bituminous material in the tank 10, where thematerial may be further heated by the stack flues 24. When ill .4 theliquid bituminous material is sufficiently heated, preferably to about350 F., the liquid is drained from outlet 12 into tank trucks forconveyance to a road paving mixing plant or into tank trucks havingdistributors for directly spraying the liquid material upon roadsurfaces.

An alternative and important use of the unit is obtained when it isstationed adjacent a road paving mixing plant where the tank 10 mayreceive liquid bituminous material from tank trucks or from steamjacketed supply conduits. The liquid bituminous material is heated tohigher temperatures by the stack flues 24, and then conveyed to themixing plant where it is bonded with gravel to form a paving material.The boiler 14 provides steam for the power plant operations of themixing plant, and primarily to supply steam to the steam-atomizingburner which pre-dries the gravel.

Even though the boiler 14 is located entirely within the tank 10,comparatively little heat is transferred from the boiler to thebituminous material within the tank. The bituminous material depends forits heat almost entirely upon the stack lines 24, which carry theexhaust gases from the boiler tubes 15 back through the tank 10subjacent to the boiler 14 and near the bottom of the tank to the stackflue header 25, where the gases are discharged through exhaust port 28.The steam generated in the boiler 14 is used almost exclusively foroperations external to the heating unit.

In cases where a more rapid rate of heating or a higher temperature isdesired Within the tank 10, the steam coils 40 located in the bottom ofthe tank may provide this additional heat from steam generated in theboiler 14 and tapped from the steam header 18 through conduit 21.

It is important that the stack fiues 24 be located be neath the boilerand near the bottom of the tank 10, in order that the tlues may begin toheat the initial portion of the liquid bituminous material as itaccumulates in the bottom of the tank 10. Furthermore, as the liquidnear the bottom of the tank becomes heated, it rises, setting up liquidconvection currents, thus creating a uniform liquid temperaturethroughout the tank.

Because of the large capacity, in the order of 20,000 gallons, and theportability of the unit, it is designed to assume semi-permanentpositions in road building operations. The unit may remain in onelocation for one or several days, being able to supply liquid bituminousmaterial at 350 F. for several hours before being refilled. When a roadbuilding operation has proceeded beyond the range of convenient supply,then the unit may be attached to a prime mover and conveyed to a newsite easily accessible to the road building operations.

Furthermore, the large capacity of the tank provides an excellentinsulation of bituminous material surrounding the boiler 14. It has beenfound that when the unit is idle during an overnight period, the drop intemperature of the material in the bottom of the tank is only about F.Consequently, about thirty minutes after the boiler is retired, the unitis capable of discharging bituminous material at approximately 350 F.From a cold start, the unit is ready to discharge bituminous material atthat temperature within one hour.

Although the number and size of the boiler tubes 15 and the stack fiues24 are not material to this invention so long as the total crosssectional area of the stack tubes 24 is equal to or exceeds the totalcross sectional area of the fire tubes 15, a satisfactory arrangementhas been found in providing the boiler with 53 2" O. D. boiler tubes and23 3" O. D. stack fiues.

The use of a compact portable heating unit for bituminous materials suchas the one described, which utilizes one source of energy to providehigh grade steam power for external power plant operations, to providesteam for other uses, and also to provide a heating supply to raise thetemperature of liquid bituminous material contained within the tank ofthe unit, results in a savings of approximately 60% of the fuelconsumption by conventional methods heretofore used employing separateenergy sources for steam power and for heating the bituminous material.Furthermore, by employing such a compact and portable heating unit,approximately a thousand manhours are conserved by the elimination of asingle dismantling and reassembling operation previously incurred inmoving pavement mixing plants and machinery from one site to another inorder to keep pace with the progress of the road paving andconstruction.

It will be apparent to those skilled in the art that various changes maybe made in the invention, without departing from the spirit and scopethereof, and therefore the invention is not limited by that which isshown in the drawings and described in the specification, but only asindicated in the appended claims.

In place of heating water to generate steam in the boiler 14, aheat-transfer medium such as mineral oil can be used in the boiler andcirculated through tank cars and the coils 40 in the bottom of the tank.Furthermore, applicants apparatus can be used to heat other fluids, suchas water, in the tank 10.

What is claimed is:

1. A heating apparatus comprising a tank containing material to beheated, a fire tube boiler containing a fluid to be heated extendingsubstantially parallel to the bottom of said tank, the heat receivingend of said boiler extending through the rear end of said tank, acombustion chamher outside the tank and communicating with the receivingend of the boiler and means for firing said combustion chamber, a gascollecting header communicating with the gas discharge end of theboiler, a plurality of fire tubes within said boiler communicating saidcombustion chamher with said header, a plurality of fines extendingalong the greater portion of the length of and within said tank, saidflues being disposed outside of and subjacent to the boiler andsubstantially parallel to and near the bottom of said tank, said fluescommunicating with said header and terminating outside the rear end ofthe tank, and means for exhausting gas from said fines.

2. A heating apparatus comprising a tank containing material to beheated, a boiler containing a heat-exchange fluid within the tank, afuel burner and a combustion chamber outside the tank, a plurality offire tubes within the boiler and communicating at their one ends withsaid combustion chamber, an exhaust header with which the other ends ofthe fire tubes communicate, a plurality of return fines outside of andbelow the boiler and Within the tank near the bottom thereofcommunicating at their one ends with the exhaust header and a stack flueheader with which said return flues communicate at their other ends.

3. The invention according to claim 2 in which the boiler, fuel burner,combustion chamber, fire tubes and return lines are horizontallydisposed.

4. The invention according to claim 2 in which the exhaust header isoutside the boiler but within the tank and the stack flue header isoutside the tank.

References Cited in the file of this patent UNITED STATES PATENTS1,116,788 Bell Nov. 10, 1914 1,350,502 Hetherington Aug. 24, 19201,558,438 Prat Oct. 20, 1925 2,136,242 Haupt Nov. 8, 1938 2,625,915Glasgow Jan. 12, 1953

